Oriental Orthodox Church
The Oriental Orthodox Church is one of the two main branches of eastern Christianity - the other is the Eastern Orthodox Church. The Oriental Orthodox Church comprises the Coptic Orthodox Church, the Armenian Apostolic Church, the Syriac Orthodox Church, the Ethiopian Orthodox Church, the Eritrean Orthodox Church, and the Malankara Orthodox Syrian Church.
What is today known as the Oriental Orthodox Church came into existence in the fifth century of the Christian era. In the fourth and fifth centuries Christian theologians disputed whether Jesus, as both fully divine and fully human, has two natures, a divine nature and a human nature, each distinct from, but very closely related to, the other (Dyophysitism) or only one nature, a divine nature which in some way includes or absorbs his humanity (Monophysitism). In 451 an ecumenical Council of bishops meeting at Chalcedon endorsed Dyophysitism and condemned Monophysitism as a heresy. However, although the Council's endorsement of Dyophysitism was accepted by all the Churches in the western half of the Roman Empire, it was not universally accepted in the eastern half. Those Churches in the eastern half which accepted the Council's decision constitute what is today known as the Eastern Orthodox Church, while those Churches which rejected the decision constitute the Oriental Orthodox Church. The main reason why these latter Churches were unwilling to accept the Council's decision was that Dyophysitism seemed to them too similar to Nestorianism, i.e., the belief that Jesus has two natures, a divine nature and a human nature, rather loosely related to one another, a doctrine which had been condemned as heretical by the ecumenical Council of Ephesus in 431. In fact, although the Oriental Orthodox Church has always rejected Dyophysitism, it denies that its position with regard to Jesus' nature(s) is properly characterised as Monophysite - and with some justice since it distinguishes its position from the best known variants of Monophysitism. It prefers its doctrine to be known as Miaphysitism rather than Monophysitism. ('Mia' (μία) is the feminine form of the Greek word for 'one', while 'mono' comes from μόνος (monos, only or single); '-physitism' and '-physite' come from φύσις (phusis, nature).)
In recent years theologians from the Oriental Orthodox Church and the Eastern Orthodox Church have reached the conclusion that the doctrinal differences between their respective Churches with regard to Jesus' nature(s) are more differences of terminology than differences of substance; and this has opened the way to moves towards a reconciliation between these two branches of eastern Christianity.